The present invention relates to a developing device for an electrophotographic image recording apparatus.
Conventionally, an image recording apparatus such as an electronic copy machine, laser beam printer and the like, has been known in which a so-called electrophotographic image forming process is employed.
In the electrophotographic image recording apparatus as described above, an electrostatic latent image is formed by exposing the uniformly charged photoconductive material provided on the circumferential surface of a photoconductive drum. The latent image is developed by applying toner onto the photoconductive material in order to form a toner image. Then the toner image is transferred onto a recording sheet, and the transferred toner image is heated/pressed and fixed thereon.
In such an electrophotographic image recording apparatus, toner filled in a toner chamber of the developing device is magnetically attracted by a developing roller and transported to a developing area. Generally, toner is supplied to the toner chamber by means of a detachable toner cartridge. When using the toner cartridge, stain to the apparatus, due to the leakage of toner, is easily prevented. Further, the toner supply can be easily replenished.
FIG. 1 shows an example of a toner cartridge 20 attached to a developing device 10. A cartridge attachment portion 13 is positioned above the toner chamber 11, to which the toner cartridge 20, filled with toner, is attached. Then the toner, accommodated in the toner cartridge 20, is allowed to fall in the toner chamber 11. In this case, after the toner is supplied to the toner chamber 11, the toner cartridge 20 becomes empty. The empty toner cartridge 20 is used as a cover for the toner chamber 11 until the a new toner cartridge, filled with toner replaces the empty toner cartridge 20.
However, as constructed above, the toner cartridge, after the toner has been transported to the toner chamber remained attached to the developing device in on empty condition. Typically, the cartridge protrudes largely from the upper surface plane of the developing device, whereby, the empty cartridge creates a large uselessly occupied space.
On the other hand, since the processing speed of the image recording apparatus has improved recently, if the capacity of the toner cartridge is relatively small, the cartridge will have to be replaced frequently. If the capacity of the cartridge is made relatively large, so that more image forming process can be done with a single toner supply, the problem resides in that the developing device as well as the toner cartridge will need to be made larger which goes against the recent tendency to make the apparatus compact.